Organic Light-Emitting Diode (OLED) displays are called next-generation display technologies because of their advantages of self-luminescence, wide viewing angle, flexibility, and so on. In a manufacturing process of the OLED displays, an organic light-emitting layer is usually formed by using an inkjet printing process. In the inkjet printing process, when droplets are dripped, each of the droplets dripped by different print heads need to be aligned with a respective one of pixels. Positioning accuracy of the droplets is currently a main technical bottleneck, and a slight deviation in the positioning of the droplets can lead to errors in an entire printing plate. As resolution of products increases and pixel size decreases, the positioning accuracy of the droplets is also higher. Therefore, printing errors caused by poor positioning are more frequent.